Control of malignant tumors in animals still remains as an unrealized goal. Within the last several decades, understanding of malignancy has made significant progress; however, conquering of the malignant disease state has not been realized.
Conventional therapy presently includes surgical excising of the tumor, local radiation therapy of the afflicted animal, and chemotherapy by administration of a chemotherapeutic agent to the animal. The death is attributable not to the primary tumor but instead to metastasis of the primary tumor to secondary sites in the host. If a primary tumor is detected early, it normally can be eliminated by surgery, radiation or chemotherapy or combinations of these. The metastatic colonies of these primary tumors, however, are exceedingly harder to detect and eliminate and the unsuccessful management of them remains a serious medical problem.
Tumors are normally classified either as benign or malignant. The malignant tumor is characterized by its ability to invade both surrounding tissue and to colonize distant sites via metastasis. Certain organs are more prone to metastasis than others. Included in this group would be the lung, the brain, the liver, the ovaries and the adrenal glands. It has further been expected that both surgery and radiation of a primary tumor in certain instances actually promote metastasis.
In view of the inability of current cancer therapy to successfully control the malignant tumor and its metastasis, a need for additional chemotherapeutic agents exists.
Similarly, for the control and management of antiviral infections, agents are currently available, but few are clinically applicable and these are only narrowly active. In this field, therefore, a need for additional chemotherapeutic agents also exists, especially for agents that have both antiviral and antitumor activity.